Decomposability of Bimodule Maps

• Autores: Christian Le Merdy, Lina Oliveira
• Localización: Mathematica scandinavica, ISSN 0025-5521, Vol. 119, Nº 2, 2016, págs. 283-292
• Idioma: inglés
• DOI: 10.7146/math.scand.a-24747
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• Resumen

  • Consider a unital $C^*$-algebra $A$, a von Neumann algebra $M$, a unital sub-$C^*$-algebra $C\subset A$ and a unital $*$-homomorphism $\pi\colon C\to M$. Let $u\colon A\to M$ be a decomposable map (i.e. a linear combination of completely positive maps) which is a $C$-bimodule map with respect to $\pi$. We show that $u$ is a linear combination of $C$-bimodule completely positive maps if and only if there exists a projection $e\in \pi(C)'$ such that $u$ is valued in $\mathit{e\mkern0.5muMe}$ and $e\pi({\cdot})e$ has a completely positive extension $A\to \mathit{e\mkern0.5muMe}$. We also show that this condition is always fulfilled when $C$ has the weak expectation property.